One of the devices for a ship which have become known for collecting the impurities on a free water surface provides a feed channel in front of the ship for scooping up a more or less thick surface layer of the water to be cleansed The thickness of the layer is determined thereby by means of a float-controlled peeling body which restricts to a larger or smaller extent the feed channel entrance opening. The solution proposed here, serving for limiting the inflow of a relatively thin oil layer that floats on the water, is disadvantaged by the fact that water is dammed up in front of the peeling body so that the dammed-up water will to some extent enter the channel after all.
Another proposal provides the entire front of a flat, open ship as an intake opening being partitioned into many small cavities which are situated next to each other and above each other and are individually openable. Here, those cavities are to be closed which are situated below the oil film so that only the relatively thin oil film itself may enter the collecting container. The same reservations are valid here because, due to water damming in front of the closed cavities, water will overflow together with the oil film thereon.